1. Field of the Present Invention
The present invention relates to a method of manufacturing a liquid discharge head having discharge ports which discharge a liquid, and a method of manufacturing a discharge port member for the liquid discharge head.
2. Description of the Related Art
A liquid discharge head can be used as an ink jet head mounted on an ink jet printer. Japanese Patent Application Laid-Open No. H03-049960 discloses a method of forming a discharge port member, having discharge ports which discharge ink and being used for an ink jet printer, by electroforming.
A method of forming a discharge port member using electroforming will be described in detail. FIG. 11 is an enlarged sectional view of portions of discharge ports and liquid flow paths in the liquid discharge head 1. A discharge port member 11 is provided with a plurality of discharge ports 12, and the discharge port member 11 is fixed to flow path walls 13 with an adhesive 16. The flow path walls 13 are arranged on the element substrate 10 having energy generating elements 14 which generate the energy for discharging ink. Liquid chambers which are regions surrounded by the flow path walls 13, the element substrate 10, and the discharge port member 11 are filled with ink. The ink within a liquid chamber is caused to fly as ink droplets from a discharge port 12 of the discharge port member 11 by the energy generated by the energy generating element 14, and adheres on a printing paper.
There are a number of methods as the method of forming the discharge ports 12 in the discharge port member 11. For example, drilling, electrical discharge machining, laser machining, electroforming, and the like are generally known. Among these methods, electroforming has an advantage that a plurality of discharge ports 12 can be formed at a low cost.
FIGS. 4A to 4C are views for describing an example in which discharge ports 12 are formed by electroforming. First, as illustrated in FIG. 4A, a resist 17 made of photosensitive resin is coated on the conductive substrate 21. Next, a mask 18 having openings is arranged on the resist 17. In addition, in the mask 18, the distance between an opening and another opening adjacent thereto (an arrow portion in FIG. 4A) is D. Then, portions of the resist 17 corresponding to the openings are exposed using exposure light 19. When the portions are subjected to development treatment, the resist 17 is developed as illustrated in FIG. 4B. In addition, the thickness of resist 17 is defined as tD. Next, when Ni (nickel) is plated on the conductive substrate 21 by electroforming, as illustrated in FIG. 4C, plated nickel 20 is stacked. At this time, a discharge port with diameter d is formed between the stacks of plated nickel 20. When the thickness (refer to FIG. 4C) of the plated nickel 20 is defined as tN, the diameter d is substantially expressed by the following expression.d≅D−2(tN−tD)  (Expression 1)
Accordingly, d is determined by the distance D between an opening and another opening adjacent thereto in the mask, the thickness tD of the resist 17, and the thickness tN of the plated nickel 20. Since tD is negligible, in the case when d is not to be changed, the thickness of the plated layer must become smaller when the distance between the discharge ports is made smaller. In other words, the discharge port member becomes thinner as the density of the discharge ports becomes higher.
Here, a flow path, which leads to a discharge port 12 of the discharge port member formed by plating, is formed by a curved surface so that the diameter thereof becomes gradually smaller toward the discharge port 12. When the discharge port member is formed in a shape such that the thickness of the member becomes smaller, it becomes difficult to make a discharge liquid droplet fly in a direction in which the liquid droplet goes straight ahead toward the substrate 101.